As its description goes, Google contacts is your online address book. But it's no ordinary address book because the Google contact cards merges the information you have for a specific contact and what that contact shares with Google online. Each profile on your online address book can contain basic information like phone numbers, email addresses, and names to extended data like job title, department, employer, and even their physical address.

With an online address book like Google contact you automatically integrate your contact list with your Google calendar, drive, gmail and other google apps throught he autocomplete function. Essentially, this feature is quite helpful in scheduling appointments, sharing documents, and sending emails to your contact list without the need to open the contact information on a separate window or tab. Further, what's great about this app is that you can sync contacts between Google apps and a mobile device and even see contacts outside of a browser.

Basically with a Google contacts app, you can have two different types of Google contacts. One is the my contacts where you can store your personal contacts as managed by you. And the second is the Google Apps directory which is a domain wide contact list managed by site administrators.